Traditionally in substrate build-up layer manufacturing, a wet desmear etching process may serve to both clean remaining laser via residue and to roughen the surface of a dielectric build-up layer for later electroless copper (Cu) adhesion. However, recent demand for finer pitch routing and high frequency data transfer integrity in high density interconnect substrates has highlighted the importance of low loss dielectric material and low interfacial surface roughness between the metal layer that results from the electroless Cu adhesion and the dielectric build-up layer.
Generally, legacy wet desmear processes may not be able to clean extremely low loss dielectric materials. One alternative process that may be used to adequately clean vias in extremely low loss dielectric materials subsequent to laser drilling of the vias may be to perform a plasma desmear process. Plasma desmear may be generally accomplished by capacitively coupled plasma (CCP), inductively coupled plasma (ICP), reactive ion etching (RIE), and/or some other type of plasma system using oxygen (O2) and/or fluorinated gases to etch organic layers of the dielectric material. While process conditions related to the plasma desmear may be optimized to reduce surface etching of the dielectric material, some etching will inevitably occur. This etching may potentially expose dielectric fillers, increase dielectric roughness, and/or potentially reduce adhesion strength to the electroless Cu.